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astik / ansible-role-variable-and-multi-instanciation

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Variable resolution within multi-instantiated role

Here are some demo relative to a "bug" in Ansible. This behavior has been encountered with multiple Ansible's versions (at least from up to 2.7.1 on macOS Mojave 10.14)

The idea is to have a role that is used multiple times with different inputs. It works well until you have a dynamic handler that depends on variable. If the variable for handler's name is defined in playbook, it works. If the variable is coming from group_vars, it fails.

As behavior is depending on where variable is set, i found it inconsistent, therefore it seems to be a bug.

The opened issue is : ansible/ansible#48537.

Here are some other issues that seems to be relative :

Also, a stackoverflow that seems to be also relative : https://stackoverflow.com/questions/25694249/ansible-using-with-items-with-notify-handler/25704162#25704162

TLDR

Extract from ansible/ansible#48466 (comment) :

Task names (including handlers) cannot depend on a host var as they need to be the same for all hosts,
it does not matter that you use the 'all' group as that is still flattened and 'per host'.

So, it clarifies the fact that variables coming from group_vars are not populated and the one from playbook or command line are.

If you need a way to make it work, check out demo 04.

Demo

Each demo are composed of a naive playbook with a very simple role test. You can test any of those :

cd xx-my-demo
ansible-playbook test.yml -i inventories/testInv

01-variable-in-playbook__SUCCESS

  • variables are defined into playbook directly
  • handler has a dynamic name ("handle inst1" and "handle inst2")
  • both notifications trigger their own handler
PLAY [servers] ****************************************************************

TASK [test : debug] ***********************************************************
ok: [localhost] => {
    "msg": "echo inst1"
}

TASK [test : command] *********************************************************
changed: [localhost]

TASK [test : debug] ***********************************************************
ok: [localhost] => {
    "msg": "echo inst2"
}

TASK [test : command] *********************************************************
changed: [localhost]

RUNNING HANDLER [test : handle inst1] *****************************************
ok: [localhost] => {
    "msg": "inst1"
}

RUNNING HANDLER [test : handle inst2] *****************************************
ok: [localhost] => {
    "msg": "inst2"
}

PLAY RECAP ********************************************************************
localhost                  : ok=6    changed=2    unreachable=0    failed=0

02-handler-with-dynamic-name__ERROR

  • same as demo 01
  • variables are moved from playbook to group_vars
  • an error occurs when execution ansible-playbook
PLAY [servers] ****************************************************************

TASK [test : debug] ***********************************************************
ok: [localhost] => {
    "msg": "echo inst1"
}

TASK [test : command] *********************************************************
ERROR! The requested handler 'handle inst1' was not found in either the main handlers list nor in the listening handlers list

03-handler-with-static-name__FAIL

  • same as demo 02
  • handler's name is now static ("handle foobar")
  • both notifications are triggered but only one handler is executed
PLAY [servers] ****************************************************************

TASK [test : debug] ***********************************************************
ok: [localhost] => {
    "msg": "echo inst1"
}

TASK [test : command] *********************************************************
changed: [localhost]

TASK [test : debug] ***********************************************************
ok: [localhost] => {
    "msg": "echo inst2"
}

TASK [test : command] *********************************************************
changed: [localhost]

RUNNING HANDLER [test : handle foobar] ****************************************
ok: [localhost] => {
    "msg": "inst1"
}

PLAY RECAP ********************************************************************
localhost                  : ok=5    changed=2    unreachable=0    failed=0

04-handler-with-dynamic-name-take2__SUCCESS

  • same as demo 03
  • handler's name is back to dynamic but with a variable that is set explicitly in the playbook ("myInstance1_from_playbook" and "myInstance2_from_playbook")
PLAY [servers] ****************************************************************

TASK [test : debug] ***********************************************************
ok: [localhost] => {
    "msg": "echo inst1"
}

TASK [test : command] *********************************************************
changed: [localhost]

TASK [test : debug] ***********************************************************
ok: [localhost] => {
    "msg": "echo inst2"
}

TASK [test : command] *********************************************************
changed: [localhost]

RUNNING HANDLER [test : handle myInstance1_from_playbook] *********************
    "msg": "inst1"
}

RUNNING HANDLER [test : handle myInstance2_from_playbook] *********************
ok: [localhost] => {
    "msg": "inst2"
}

PLAY RECAP ********************************************************************
localhost                  : ok=6    changed=2    unreachable=0    failed=0

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